Wet brushing of woven asbestos fabric



July 25, 1961 WET H. E. SUNBURY BRUSHING OF' WOVEN ASBESTOS FABRIC FiledJune 16, 1955 United States This invention relates to a method oftreating fabrics formed predominantly of asbestos bers to make thefabric smoother, and whiter, and to give it a softer hand :and theappearance of a ner weave than are characteristic of the conventionalasbestos fabrics of the same construction made heretofore. The inventionalso relates to the product produced by the hereinafter describedmethod.

Because of the nature of asbestos bers and the relatively short lengthof the commercially available ber, conventional fabrics made heretoforeof asbestos bers are relatively coarse, even though a percentage of acarrier ber, for example, cotton, is included in the ber blend, which iscustomarily done in commercial fabrics. For example, a fabric weighingapproximately 14 ounces per square yard, and woven with 30 warp threadsper inch and 24 picks per inch of 23 cut asbestos-cotton blend yarns, isconsidered a lightweight asbestos fabric. By comparison with mostfabrics made of other textile bers such as cotton, wool or the syntheticyarns, however, this is a coarse weave.

The natural color of asbestos ber in the form in which it isconventionally used in textiles, is grey-White, and sometimes it has atinge of brown. This color is not noticeably changed by conventionaltextile bleaching.

A slight further whitening of an asbestos fabric may be obtained bycoating or impregnating it with a liquid dispersion of a white pigment,for example, titanium dioxide. However the degree of whitening which maybe obtained by such pigmentation is limited particularly because of theend use requirements of the fabric. A binder must be used to hold thepigment on the fabric, and the addition of the pigment in such a binderto the fabric causes a loss of exibility in the fabric. For manyfabrics, it is required that they retain their flexibility substantiallyunchanged, and consequently this method of whitening the fabrics cannotbe employed. Even when it is permissible to use this method of whiteningfabrics, the expense of doing it increases the cost of the nishedproduct, and the nished product is inferior because of its diminishedflexibility.

It is a primary object of this invention to provide a method whereby aconventional asbestos fabric can be idatent made smoother and whiter,yet in which the nished prods uct will have a softer hand and theappearance of a ner weave than a fabric of the same construction but nottreated in accordance with this invention. It is a further object ofthis invention to provide a fabric having these characteristics. Still afurther object of this invention is to provide a relatively inexpensivemethod of improving the appearance of asbestos fabrics.

In accordance with this invention there is provided an asbestos fabricformed of interlaced yarns composed predominantly of asbestos fibers.For example, a conventional woven asbestos fabric formed of yarnscomprising a major proportion of asbestos bers and a small proportion ofa carrier ber, such as the conventional cotton asbestos blends, isprovided. This asbestos fabric is then thoroughly wetted as by immersingit in an aqueous bath. After the fabric has been thoroughly wetted andbefore it has had an opportunity to dry and before it is otherwisetreated, the fabric is brushed. This may be done in numerous ways suchas by hand brushing, mechanical brushing, etc., and in one practicalcommercial embodiment the fabric is advanced in contact with l y2,993,26l Patented July as, 1951 two rapidly rotating cylindricalbrushes that are positioned to brush each face of the fabric. After thefabric has been thoroughly brushed, it is dried, preferably withoutfurther treatment and preferably without squeezing any water out of thefabric. Conveniently the fabric may be dried by advancing it through atenter drier.

The product after it has dried will be found to possess a greatlyenhanced luster and whiteness. The weave of the fabric will besubstantially closed up so that the nished product has the appearance ofa much ner weave than a fabric of precisely the same construction butnot treated in accordance with this invention and the fabric appears tobecome more supple after treatment.

It appears that by the wet brushing operation, many of the short lengthsof asbestos bers which normally protrude from the yarns are broken offand deposited in the spaces between the interlaced yarns. Apparentlythere is also some breakage of bers in the yarns, because the quantityof short bers deposited in the interstices between the yarns appears tobe greater than that of the originally protruding ends. Upon drying, thedeposited bers adhere tightly to each other and to the interlaced yarns,for the fabric will withstand a considerable degree of distortion andexing without dislodging them.

Although the deposited bers are rather rmly held in the fabric, they canbe dislodged by severely distorting the fabric. This can besubstantially prevented by the use of a small amount of binder, such asstarch, thermosetting resins, thermoplastic resins, etc. Desirablythebinder may be incorporated in the fabric at the wetting bath byincluding in the bath a small proportion of binder, such as thatdisclosed in my U.S. Letters Patent 2,382,830, granted August 14, y1945.

It is characteristic of fabrics produced in accordance with thisinvention that the bers deposited in the interstices between theinterlacings of the yarns bridge these interstices to such an extentthat the air permeability of a fabric in accordance with this inventionis reduced as much as 40 to 90% and more from that possessed by a fabricof identical construction but not treated in accordance with thisinvention. Because of this bridging of the interstices, the fabric hasthe appearance of a uer Weave after treatment. The treatment alsoenhances the natural luster of the asbestos bers. A fabric produced inaccordance with this invention has a markedly increased whiteness andluster as compared with a fabric of identical construction but untreatedin accordance with this invention. The product of this invention alsohas a smooth, white satiny appearance reflecting highlights. Thebrushing apparently also removes or covers up most of the bits offoreign matter normally accompanying a cotton carrier ber, andconsequently any blemishes due to this foreign matter are not soapparent in the nished product. The nished product also possesses aremarkably soft hand. It is essential to achieve the ends of thisinvention that the asbestos yfabric be brushed while wet and thereafterdried. Wetting and drying alone produces relatively little change in theappearance of the fabric; the protruding ber ends are to some extentheld down against the yarns, but they do not noticeably tend to bridgethe interstices. Brushing the fabric while dry merely increases thefuzziness of the fabric, presumably by breaking some of the bound bersin the yarns.

Preferably none of the water is squeezed out of the fabric either beforeor after brushing. If the fabric is squeezed before being brushed, theeffects of the brushing are reduced, and if it is squeezed after beingbrushed,

part of the short asbestos bers on the surface of theY fabric adhere tothe squeeze rolls. It appears that the usefulness of the process isconned to fabrics formed of interlaced yarns formed predominantly ofasbestos bers. I

The product may be used in any application in which it is not subjectedto mechanical stresses sufliciently severe to dislodge the depositedfibers. The product is especially useful in those applications whichrequire a smooth surfaced asbestos fabric, and in those applicationswhere the appearance `of the fabric and its hand is important. Forexample, the product is especially useful in such applications as coverfabrics for home ironing boards, commercial laundry fabrics, oven mitts,pot holders, safety clothing and insulation jacketing for steam pipesand air ducts.

In many applications it will be found desirable to calender the asbestosfabric after processing in accordance with this invention and after ithas been thoroughly dried.

For a better understanding of the nature of this invention, referenceshould be had to the following detailed description `of specificembodiments thereof when read in conjunction With the accompanyingdrawings forming a part of this application.

In the drawings:

FIG. l is a schematic side elevation of apparatus which may be employedto practice the method of this invention and illustrating this method;

FIGS. 2 and 4 are plan views of small samples of fabric treated inaccordance with this invention; and

FIGS. 3 and 5 are plan views of fabrics identical with FIGS. 2 and 4respectively but which have not been treated in accordance with thisinvention.

In the drawings there is illustrated one form of apparatus suitable forcarrying out the method in accordance with this invention. A suitableasbestos fabric F is passed in open width through an aqueous bath W. Thefabric lF is supported by a beam lrotatably mounted adjacent the tank 11containing the bath W. The fabric F is unrolled from the beam 10 bypulling it forward from the beam 10 to pass over a free running `roller12 and be directed downwardly into the bath W where it is thoroughlywetted. In the bath W, the fabric F passes under the spaced free runningrollers 13. After the thoroughly wetted fabric F leaves the bath W, itpasses over the lfree running roller 14 and is directed to a pair ofrotatably driven cylindrical brushes 15, 16.

In the embodiment shown, these brushes 15, 16 are spaced vertically andhorizontally from each other so that the fabric may be led thereabout ina tortuous path to have one side of the fabric wrapped partly about thefirst brush and the other side of the fabric wrapped partly about thesecond brush 16. Using this arrangement of brushes, theV fabric F isthoroughly brushed on both sides by the bristles 17 of the brushes 15,16.

As illustrated in FIG. 1, a small roll B of wet ibers may accumulateahead of the brushing rolls. This roll of bers is very desirable intreating the fabrics in accordance with this invention as this beadVforms an, excess supply of bers from which Vfibers may be forced intothe interstices of the fabric. Such a roll of fibers can be achieved bya suitable setting of the brush 15 v After the fabric has beenthoroughly brushed it is then dried as by advancing it through a tenterdrier shown schematically at 18. 'Ihereafter the fabric may be wound ina roll 19 for storage or use. However if desirable the fabric may becalendered after it has dried, and in the drawing there is shown indot-dash lines a pair of calender rolls 20, 21 that are adapted tocalender the fabric as it emerges from the tenter drier to furthersmooth the product.

The aqueous bath W may be a water bath, and Vdesirably may have addedthereto a small percentage of binder adapted to hold the small fibers inthe fabric as heretofore described. A water bath containing 7.5% byweight of polymethymethacrylate binder-has been found tov be highlysatisfactory.

VThe type of brush, direction of rotation, speed of brushing, and thepressure of the fabric against'f the brushes may bevaried. For example,the fabric may be brushed by moving, iiexible, vanes extending the widthof the fabric; long narrow strips of rubber fixed to rotating cylindersmay be used. Preferably however brushes having long, soft bristles areemployed to brush the fabric at high brushing speed with light contactwith the fabric. An apparat-us employing cylindrical brushes of 7 inchesoverall diameter, containing 7.85 tufts per square inch, each squareinch having approximately 4700 nylon bristles of 0.008 inch in diameterand 11/2 inches in length, which brushes rotate at a speed of 400 to 600revolutions per minute, has proved highly satisfactory. Desirably onebrush may rotate at a slightly greater speed than, or in oppositedirection to, the other so as to produce a face for the fabric havingdifferent characteristics from the back of the fabric.

The fabric produced in accordance with this method has the intersticesprovided by the interlacings of the yarns forming the same partially orcompletely bridged by short asbestos fibers which `give to the fabricthe appearance of a finer structure and markedly increases the whitenessof the fabric. The brushing also has an incidental advantage in that itmay tend to eliminate unevenness in the interlacing, such as theunevenness of woven fabrics which is commonly known as reed marks.

Characteristically the air permeability, as tested in accordance withthe well known Frazier Permeability test, of fabric treated inVaccordance with this invention is reduced as much as 40% to 90% andmore from that possessed by a fabric of the identical construction butuntreated in accordance herewith, because of the bridging of theinterstices of the fabric by the short asbestos fibers.

As further illustrating the products produced by this method, theyfollowing specific examples are given.

Table I Fabric Analysis A B O D E Weight/square yardoz 27. 33 22. 15 15.72 13. 42 11. 5 No. Warp thds./inch 31 24 16 36 18. 7 No. Fillingthds./ine 30 12 17 19 18 Weave Sateen Plain Plain Twill Plain Size WarpYarn 22/2 22/2 27/2 51/2 42/2 Size Filling Yarn 42/2 22/2 27/2 51/2 42/2Air Permeability 1' (off 100m) 30. 5 96. 0 174 8 217 Air Permeability(after wet brushing) 1. 0 28:5 4. 1 5. 5 2.3 Reduction in airpermeability.- percent.. 96. 6 70. 2 97. 7 93. 7 98. 8

1 Frazier method (cubic feet/square foot/minute).

The fabrics of the above table were treated using a water bathcontaining the binder. disclosed, the apparatus illustrated in thedrawings and the preferred nylon brushes described above. The brushesare arranged to have the fabric in contact with each brush through about3 inches of their circumference withV the fabric displaced about 'l1/2from ya straight line. The tension was adjusted on the fabric tocompress the nylon bristles about An important characteristic of thefinished product produced in accordance with the method of thisinvention isrits decreased air permeability as shown inTable I.Qharacteristically the air permeability is reduced 40% and more, and formany fabrics it is reduced `as much as and more'. The precise value ofthe reduction in air permeability will vary with such factors as `fabricWeave, yarn employed etc. The degree of brushing may be varied toachieve different desired end products, and this will also affect airpermeability. I'he fabrics shown in the tables had their airpermeability ,reduced from 701% (Fabric B) vto in excess of 98% (FabricE), and most had the permeability reduced more than 90%. Y

, Anotherrcharacteristic change wrought in the lfabrics after treatmentin accordance with this invention is an increase in the abrasionresist-ance of the fabrics. This is shown in the following table whichshows the abrasion resistance of some of thefabrics of TablepI, asmeasured onthe.U.S.v Testing. Co. Weartester'developed by the U.S.

It appears this increase in abrasion resistance may be due to thefilling up of the interstices of the fabric.

A most-important characteristic of the product is the increase ofwhiteness of the fabric over the same `fabric untreated. FIGS. 2-5 ofthe drawing partially illustrate this change in appearance of theproduct. These gures are full scale drawings of substantially the samesize specimens of fabric which drawings were prepared from photographsof the lfabric resting on a dark background. FIG. is a view of thefabric untreated, and as will be apparent the dark background showsthrough the Ifabric in the interstices of the weave. Unevenness of theweave also is apparent as at 31. Referring to FIG. 4 there is shown anidentical view of a specimen of the same fabric shown in FIG. 2 buttreated in accordance with this invention. By a comparison of FIGS. 4and 5, and despite the shadows produced in printing the drawing from thephotograph, it will be noted that the apparent whiteness of the productis greatly enhanced, the weave appears to be made much finer and-blemishes in the fabric due to weaving have apparently disappeared.Although the fabric of FIG. 5 may appear darker than the fabric of FIG.4 because the dark background shows through the interstices of thefabric, this method of illustration indicates with considerable accuracythe change in appearance wrought in the fabric itself. In the fabricitself, voids would be visible in the fabric of FIG. 4 which would tendto show the fabric darker as illustrated. Similarly the shadowsappearing in these interstices make the fabric appear grayer so that itappears a dull gray as compared with the bright white fabric appearanceachieved after treating it in accordance with this invention asillustrated in FIG. 5. Although the showings of FIGS. 2-5 arephotographic in character, it is not possible to reproduce accuratelythe increased whiteness which is achieved in the fabric and whichapparently is due to the effect of brushing on the asbestos fibersthemselves in the fabric. It appears that these bers are whitenedsomewhat so that the overall whiteness of the finished product isgreatly enhanced by the treatment in accordance with this invention.

FIGS. 2 and 3 are views similar to FIGS. 4 and 5 but of a more openconstruction of fabric. Similar dark areas will be noted in the fabricof FIG. 3, as appear in the fabric of FIG. 5, and by comparing FIG. 2with FIG. 3 it will be noted that these dark areas are not present inthe nished product.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A method of producing asbestos fabrics which comprises providing afabric formed of interlaced yarns made predominantly of asbestos bers,wetting said fabric, brushing the fabric continuously while wet andthereafter drying 'the fabric.

2. A method of producing asbestos fabrics which comprises providing afabric formed of interlaced yarns made predominantly of asbestos bers,wetting the fabric, depositing a binder on the fabric, brushing thefabric continuously While wet and thereafter drying the fabric.

3. A method in accordance with claim 2 including the step of calenderingthe fabric after it has been dried.

4. A method of producing asbestos fabrics which comprises, providing awoven asbestos fabric of warp and weft yarns made predominantly ofasbestos bers, Wetting the fabric by advancing the fabric through anaqueous lbath, brushing the fabric continuously while wet and thereafterdrying the fabric.

5. A'method in accordance with claim 4 wherein the fabric is brushed byadvancing the fabric as it leaves the aqueous' bath in continuouscontact under substantial pressure with rotating cylindrical brushes.

6. A method in accordance with claim 4 wherein the fabric is advancedthrough an aqueous bath containing a binder capable of binding any freeasbestos bers to the fabric.

7. An asbestos fabric formed of interlaced yarns made predominantly ofasbestos bers, said fabric having asbestos bers disposed in theinterstices between said interlaced yarns to close up said intersticessufficiently to reduce the air permeability of said fabric to a valuethat is less than 60% that possessed by the same fabric off-the-loom,said bers having been deposited in the interstices by brushing thefabric when Wet.

8. A smooth surfaced, lustrous asbestos fabric formed of interwoven warpand weft yarns made predominantly of asbestos bers, and bers from saidyarns disposed in the interstices between the warp and weft yarns toclose up the interstices of said fabric sufficiently to reduce the airpermeability of said fabric to a value that is less thanl 60% Jihatpossessed by the same fabric off-the-loorn, said bers having beendeposited in the interstices by brushing the fabric when wet.

9. A 'smooth' surfaced lustrous asbestos fabric formed of interwovenWarp and weft yarns formed predomil nantly of asbestos fibers, and bersfrom said yarns filling the interstices of said fabric sufficiently toclose up and obscure the weave of the fabric sufficiently to reduce theair permeability of said fabric to a value that is less than 10% thatpossessed by the same fabric off-the-loom, said said fibers having beendeposited in the interstices by brushing the fabric when wet.

10. A smooth surfaced asbestos fabric formed of interwoven warp and weftyarns formed predominantly of asbestos fibers, and fibers from saidyarns being brushed into the interstices between said yarns, said fibersobscuring the weave of said fabric to give the fabric an appearance of afiner weave than that possessed by the fabric off-the-loom, the surfaceof said fabric reflecting highlights, said fibers having been depositedin the interstices by brushing the fabric when wet.

11. A method of producing asbestos fabrics which comprises providing afabric woven of warp and weft yarns made predominantly of asbestos bers,wetting said fabric with water containing a small percentage by weightof a binder adapted to bind bers in the fabric, while rthe fabric is Wetadvancing at least one of its surfaces continuously in contact with abrush of fieXible bristles rotating to brush said fabric as it passesthe brush, and thereafter drying said fabric.

12. A method of producing asbestos fabrics which comprises providing afabric woven of Warp and weft yarns made predominantly of asbestos bers,wetting said fabric with water containing a small percentage by weightof a binder adapted to bind bers in the fabric, while the fabric is wetadvancing at least one of its surfaces in contact with and partiallyWrapped about a brush of flexible bristles rotating in a directioncounter to the fabric advance to brush said fabric as it passes Ithebrush, maintaining a roll of wet fibers brushed from the fabric in thenip between the fabric land brush where rthe fabric advances to thebrush, and drying the fabric after it has been brushed.

13. A method of producing asbestos fabrics which comprises providing afabric woven of warp and weft yarns made predominantly of asbestosfibres, wetting said fabric with water containing a small percentage byWeight of a binder adapted to bind bers in the fabric, while the fabricis wet advancing it under tension so that it has an upper surface incontact with and partially Wrapped about a brush of exible bristlesseveral inches in di- '7 arneter rotating at several hundred r.p.m. in adirection counter to the fabric advance to brush said fabric as itpasses the brush, maintaining a roll of wet fibres brushed from 'thefabricin the nip between the fabric and said brush where the fabricadvances to the brush, brushing the lower surface of said fabric byWrapping said fabric partially .about a brush of flexible bristlesseveral inchesl in diameter rotating at several hundred r.p.rn. in adirection counter to the fabric advance, and drying the fabric after ithas been brushed.

`14. A method of `producing asbestos fabrics which comprises providing afabric woven of warp and weft yarns made predominantly of asbestosfibers, wetting said fabric with'water containing a small percentage byweight of a binder adapted to bind fibres in the fabric, while the`fabric is wet advancing said fabric u nder tension so that it has anupper surface in contact with and partially wrapped about a bmsh offlexible bristles several inches in diameter rotating at several hundredrpm. in a direction counter to the fabric advance to brush said fabricas it passes the brush, maintaining a roll of wet fibres brushed fromthe fabric in the nip between the fabric and said brush where the fabricadvances to the brush, brushing the lower surface of said fabric bywrapping said fabric partially about a brush of flexible bristlesseveral inches in diameter rotating at several hundred r.p.rn. in adirection counter to the fabric advance, drying the fabric after it hasbeen brushed, and calendering the brushedrfabric.

15. A method of producing asbestos fabrics which comprises providinga'fabric formed of interlaced yarns made predominantly of asbestosfibres, -wetting said fabric, while the fabric is wet advancing at leastone of its Surfaces in contact with a ,rotating brash t9 brush VSaidcomprises providing a fabric woven of warp and weft` yarns madepredominantly of asbestos fibers, applying water to said fabric, whilethe fabric bears the water contacting at least one of its surfaces witha brush of exible bristles rotating to brush said fabric as it passesthe brush, and thereafter drying said fabric.

17. A method of producing asbestos fabrics which comprises providing afabric woven of Warp and weft yarns made predominantly of asbestosfibers, applying water to said fabric, advancing the fabric with atleast one of its surfaces continuously in cont-act with ay rotatingbrush of flexible bristles to brush said fabric While it carries thewater as it passes the brush, and thereafter drying said fabric.

References Cited in the le of this patent UNITED STATES PATENTS

